GB2124037A

GB2124037A - Methods of forming patterns on substrates

Info

Publication number: GB2124037A
Application number: GB08319149A
Authority: GB
Inventors: Alan Howard Nott
Original assignee: General Electric Co PLC
Current assignee: General Electric Co PLC
Priority date: 1982-07-19
Filing date: 1983-07-15
Publication date: 1984-02-08
Also published as: GB2124037B; GB8319149D0

Abstract

A method of forming a pattern of material on the surface of a substrate comprising mechanically etching a groove of the required pattern in the surface of the substrate and filling the groove with the material. The groove is preferably etched by means of a laser beam which is caused to travel over the substrate under microprocessor control. Alternatively a large area ion beam may be directed onto the substrate through a mask.

Description

SPECIFICATION Methods of forming patterns on substrates This invention relates to methods of forming patterns on substrates.

In the fabrication of electronic devices there is frequently a requirement to form a pattern of material on a substrate. The pattern typically forms interconnections between components of the device but may alternatively serve another purpose, for example, as a resistor, as an electrode of a capacitor, an acoustic wave or other transducer, or as a dielectric or ferromagnetic element.

Such patterns are conventionally formed either on the substrate surface directly by some printing process, or the like, or by deposition of a layer of the required material on the substrate surface and selective etching of the layer through a mask formed by photolithography.

It is an object of the present invention to provide a novel method of forming such a pattern on a substrate.

According to the present invention a method of forming a pattern of material on the surface of a substrate comprises mechanically etching a groove of the required pattern in the surface of the substrate and filling the groove with said material.

Preferably said groove is formed by directing onto the substrate surface a beam capable of etching the surface of the substrate.

In one embodiment of the invention said groove is formed by directing onto a localised region of the substrate surface a beam capable of mechanically etching the surface of the substrate e.g. a laser beam, and tracking the beam along a path corresponding to the required pattern.

Alternatively the groove may be formed by directing a relatively large area beam, e.g. an ion beam, onto the substrate surface through a mask defining the required pattern.

One method in accordance with the invention will now be described, by way of example.

The purpose of the method is to form an electrically conductive pattern on one main face of a planar ceramic substrate.

Firstly, the substrate is machined flat on both sides.

The substrate is then subjected to a coarse cleaning process, the primary object of which is to remove wax.

Using a commercially available microprocessor controlled YAG laser beam etching machine, a groove of the required pattern is then etched in one face of the substrate, the beam being directed onto the substrate and caused to travel thereover under microprocessor control with the laser beam set so as to produce a groove of the desired width and depth, with a minimum of debris.

After a further coarse cleaning process and firing of the substrate at about 850 C, the groove in the substrate is filled with a conductive metal paste of the kind used in fabrication of thick film circuits by printing processes.

After allowing ten minutes for settling of the groove filling, the substrate is dried and the paste solvents driven off by heating at about 125 C for 10 to 15 minutes, and the substrate is then fired again at 850 C.

The steps subsequent to coarse cleaning after groove etching are then repeated until the groove is completely filled and the substrate surface is then carefully machined to remove excess material.

Finally, the substrate is washed to remove wax and any remaining debris.

It has been found that with a method according to the invention better defined patterns and lines of narrower widths can be obtained than with comparable known processes.

Further, the method is compatible with known techniques of forming thick film circuit components.

A further feature of a method according to the invention is that since the lines of the pattern are formed in grooves in the substrate, the substrate is better able to act as a sink for heat generated in the lines. Moreover, by control of the depth of the grooves in which the lines of a pattern are formed, the method enables the depths of the lines of the pattern to be controlled, e.g. to enhance the substrate heat sink effect. Variation of the depth of the lines in a pattern formed by the above-mentioned conventional methods is virtually impossible.

It will be understood that whilst in the particular method described by way of example an electrically conductive pattern is formed, by use of appropriate other filling materials, based on glass or other dielectric materials, on ferromagnetic materials, or on electrically resistive materials, other kinds of pattern may easily be produced.

Whilst in the example described above a pattern is formed on one side only of a substrate, it will be appreciated that in other embodiments of the invention patterns may be formed on both sides of a substrate.

It will be understood that whilst a controlled laser beam is used to form the groove in the substrate in the embodiment of the invention described by of example, other methods of mechanically etching the groove may be used in other methods in accordance with the invention. In one such method a large area ion beam of cross-sectional area at least equal to the area of the substrate surface on which a pattern is to be formed is directed onto the substrate surface through a mask defining the required pattern. The mask suitably consists of stainless steel.

Claims

1. A method of forming a pattern of material on the surface of a substrate comprising mechanically etching a groove of the required pattern in the surface of the substrate and filling the groove with said material.

2. A method according to Claim 1 wherein said groove is formed by directing onto the substrate surface a beam capable of etching the surface of the substrate.

3. A method according to Claim 1 wherein said groove is formed by directing onto a localised region of the substrate surface a beam capable of mechanically etching the surface of the substrate e.g. a laser beam, and tracking the beam along a path corresponding to the required pattern.

4. A method according to Claim 3 wherein said beam is a laser beam.

5. A method according to Claim 1 wherein said groove is formed by directing a relatively large area beam onto the substrate surface through a mask defining the required pattern.

6. A method according to Claim 5 wherein said beam is an ion beam.

7. A method according to any preceding claim wherein said groove is filled by substantially filling the groove with the material in the form of a paste, firing the substrate, and removing excess material, and repeating these steps until, after firing, the groove is substantially completely filled.

8. A method according to any preceding claim wherein said material is an electrically conductive material.

9. A method according to any preceding claim wherein said substrate consists of a ceramic material.

10. A method of forming a pattern of material on the surface of a substrate substantially as hereinbefore described by way of example.

11. A substrate having a pattern of material on a surface thereof formed by a method according to any preceding claim.

12. A substrate according to Claim 11 wherein the pattern is an electrically conductive pattern.